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Intel x86 SSE SIMD 指令入门

发布于 2024-08-04 12:05:13 字数 413 浏览 9 评论 0原文

我想了解有关使用 SSE 的更多信息。

除了明显阅读英特尔® 64 和 IA-32 架构软件开发人员手册之外，还有哪些学习方法手册？

主要是我有兴趣使用 GCC X86 内置函数。

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王权女流氓 2024-08-11 12:05:13

首先，我不建议使用内置函数 - 它们不可移植（跨同一体系结构的编译器）。

使用内在函数，GCC 在将 SSE 内在函数优化为更优化的代码方面做得非常出色。您始终可以查看程序集并了解如何充分利用 SSE。

内部函数很简单 - 就像普通函数调用一样：

#include <immintrin.h>  // portable to all x86 compilers

int main()
{
    __m128 vector1 = _mm_set_ps(4.0, 3.0, 2.0, 1.0); // high element first, opposite of C array order.  Use _mm_setr_ps if you want "little endian" element order in the source.
    __m128 vector2 = _mm_set_ps(7.0, 8.0, 9.0, 0.0);

    __m128 sum = _mm_add_ps(vector1, vector2); // result = vector1 + vector 2

    vector1 = _mm_shuffle_ps(vector1, vector1, _MM_SHUFFLE(0,1,2,3));
    // vector1 is now (1, 2, 3, 4) (above shuffle reversed it)
    return 0;
}

使用 _mm_load_ps 或 _mm_loadu_ps 从数组加载数据。

当然还有更多的选择，SSE 真的很强大，而且在我看来相对容易学习。

另请参阅 https://stackoverflow.com/tags/sse/info 了解一些指南链接。

First, I don't recommend on using the built-in functions - they are not portable (across compilers of the same arch).

Use intrinsics, GCC does a wonderful job optimizing SSE intrinsics into even more optimized code. You can always have a peek at the assembly and see how to use SSE to it's full potential.

Intrinsics are easy - just like normal function calls:

#include <immintrin.h>  // portable to all x86 compilers

int main()
{
    __m128 vector1 = _mm_set_ps(4.0, 3.0, 2.0, 1.0); // high element first, opposite of C array order.  Use _mm_setr_ps if you want "little endian" element order in the source.
    __m128 vector2 = _mm_set_ps(7.0, 8.0, 9.0, 0.0);

    __m128 sum = _mm_add_ps(vector1, vector2); // result = vector1 + vector 2

    vector1 = _mm_shuffle_ps(vector1, vector1, _MM_SHUFFLE(0,1,2,3));
    // vector1 is now (1, 2, 3, 4) (above shuffle reversed it)
    return 0;
}

Use _mm_load_ps or _mm_loadu_ps to load data from arrays.

Of course there are way more options, SSE is really powerful and in my opinion relatively easy to learn.

See also https://stackoverflow.com/tags/sse/info for some links to guides.

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唐婉 2024-08-11 12:05:13

由于您要求提供资源：

将 SSE 与 C++ 结合使用的实用指南：关于如何使用 SSE 的良好概念概述有效地使用 SSE，并举例说明。

MSDN 编译器内部函数列表：供所有人参考你的内在需求。这是 MSDN，但几乎这里列出的所有内在函数都受到 GCC 和 ICC 的支持。

Christopher Wright 的 SSE 页面：有关 SSE 操作码含义的快速参考。我猜英特尔手册可以提供相同的功能，但速度更快。

最好用内在函数编写大部分代码，但请检查编译器输出的 objdump 以确保它生成有效的代码。 SIMD 代码生成仍然是一项相当新的技术，编译器在某些情况下很可能会出错。

回复收藏 0 原文

缱绻入梦 2024-08-11 12:05:13

我发现阿格纳·福格博士的研究和研究优化指南非常有价值！他还有一些图书馆和图书馆。我还没有尝试过的测试工具。
http://www.agner.org/optimize/

回复收藏 0 原文

戈亓 2024-08-11 12:05:13

第 1 步：手动编写一些程序集

我建议您首先尝试手动编写自己的程序集，以便在开始学习时准确地查看和控制发生的情况。

那么问题就变成了如何观察程序中发生了什么，答案是：

GDB
使用 C 标准库来 print 和 assert 东西

自己使用 C 标准库需要一点点工作，但没什么。我在 Linux 上的测试设置的以下文件中很好地为您完成了这项工作：

例如， h" rel="nofollow noreferrer">lkmc.h
lkmc.c
lkmc/x86_64.h

使用这些帮助程序，然后我开始学习基础知识，例如：

将数据加载到内存或从内存存储到 SSE 寄存器中
添加不同大小的整数和浮点数断言
结果是我所期望的

addpd.S

#include <lkmc.h>

LKMC_PROLOGUE
.data
    .align 16
    addps_input0: .float 1.5, 2.5,  3.5,  4.5
    addps_input1: .float 5.5, 6.5,  7.5,  8.5
    addps_expect: .float 7.0, 9.0, 11.0, 13.0
    addpd_input0: .double 1.5, 2.5
    addpd_input1: .double 5.5, 6.5
    addpd_expect: .double 7.0, 9.0
.bss
    .align 16
    output:       .skip 16
.text
    /* 4x 32-bit */
    movaps addps_input0, %xmm0
    movaps addps_input1, %xmm1
    addps %xmm1, %xmm0
    movaps %xmm0, output
    LKMC_ASSERT_MEMCMP(output, addps_expect, $0x10)

    /* 2x 64-bit */
    movaps addpd_input0, %xmm0
    movaps addpd_input1, %xmm1
    addpd %xmm1, %xmm0
    movaps %xmm0, output
    LKMC_ASSERT_MEMCMP(output, addpd_expect, $0x10)
LKMC_EPILOGUE

GitHub 上游。

paddq.S

#include <lkmc.h>

LKMC_PROLOGUE
.data
    .align 16
    input0:       .long 0xF1F1F1F1, 0xF2F2F2F2, 0xF3F3F3F3, 0xF4F4F4F4
    input1:       .long 0x12121212, 0x13131313, 0x14141414, 0x15151515
    paddb_expect: .long 0x03030303, 0x05050505, 0x07070707, 0x09090909
    paddw_expect: .long 0x04030403, 0x06050605, 0x08070807, 0x0A090A09
    paddd_expect: .long 0x04040403, 0x06060605, 0x08080807, 0x0A0A0A09
    paddq_expect: .long 0x04040403, 0x06060606, 0x08080807, 0x0A0A0A0A
.bss
    .align 16
    output:       .skip 16
.text
    movaps input1, %xmm1

    /* 16x 8bit */
    movaps input0, %xmm0
    paddb %xmm1, %xmm0
    movaps %xmm0, output
    LKMC_ASSERT_MEMCMP(output, paddb_expect, $0x10)

    /* 8x 16-bit */
    movaps input0, %xmm0
    paddw %xmm1, %xmm0
    movaps %xmm0, output
    LKMC_ASSERT_MEMCMP(output, paddw_expect, $0x10)

    /* 4x 32-bit */
    movaps input0, %xmm0
    paddd %xmm1, %xmm0
    movaps %xmm0, output
    LKMC_ASSERT_MEMCMP(output, paddd_expect, $0x10)

    /* 2x 64-bit */
    movaps input0, %xmm0
    paddq %xmm1, %xmm0
    movaps %xmm0, output
    LKMC_ASSERT_MEMCMP(output, paddq_expect, $0x10)

LKMC_EPILOGUE

GitHub 上游< /a>.

第 2 步：编写一些内在函数

但是，对于生产代码，您可能希望使用预先存在的内在函数而不是原始程序集，如以下所述：https://stackoverflow.com/a/1390802/895245

所以现在我尝试将前面的示例转换为具有内在函数的或多或少等效的 C 代码。

addpq.c

#include <assert.h>
#include <string.h>

#include <x86intrin.h>

float global_input0[] __attribute__((aligned(16))) = {1.5f, 2.5f, 3.5f, 4.5f};
float global_input1[] __attribute__((aligned(16))) = {5.5f, 6.5f, 7.5f, 8.5f};
float global_output[4] __attribute__((aligned(16)));
float global_expected[] __attribute__((aligned(16))) = {7.0f, 9.0f, 11.0f, 13.0f};

int main(void) {
    /* 32-bit add (addps). */
    {
        __m128 input0 = _mm_set_ps(1.5f, 2.5f, 3.5f, 4.5f);
        __m128 input1 = _mm_set_ps(5.5f, 6.5f, 7.5f, 8.5f);
        __m128 output = _mm_add_ps(input0, input1);
        /* _mm_extract_ps returns int instead of float:
        * * https://stackoverflow.com/questions/5526658/intel-sse-why-does-mm-extract-ps-return-int-instead-of-float
        * * https://stackoverflow.com/questions/3130169/how-to-convert-a-hex-float-to-a-float-in-c-c-using-mm-extract-ps-sse-gcc-inst
        * so we must use instead: _MM_EXTRACT_FLOAT
        */
        float f;
        _MM_EXTRACT_FLOAT(f, output, 3);
        assert(f == 7.0f);
        _MM_EXTRACT_FLOAT(f, output, 2);
        assert(f == 9.0f);
        _MM_EXTRACT_FLOAT(f, output, 1);
        assert(f == 11.0f);
        _MM_EXTRACT_FLOAT(f, output, 0);
        assert(f == 13.0f);

        /* And we also have _mm_cvtss_f32 + _mm_shuffle_ps, */
        assert(_mm_cvtss_f32(output) == 13.0f);
        assert(_mm_cvtss_f32(_mm_shuffle_ps(output, output, 1)) == 11.0f);
        assert(_mm_cvtss_f32(_mm_shuffle_ps(output, output, 2)) ==  9.0f);
        assert(_mm_cvtss_f32(_mm_shuffle_ps(output, output, 3)) ==  7.0f);
    }

    /* Now from memory. */
    {
        __m128 *input0 = (__m128 *)global_input0;
        __m128 *input1 = (__m128 *)global_input1;
        _mm_store_ps(global_output, _mm_add_ps(*input0, *input1));
        assert(!memcmp(global_output, global_expected, sizeof(global_output)));
    }

    /* 64-bit add (addpd). */
    {
        __m128d input0 = _mm_set_pd(1.5, 2.5);
        __m128d input1 = _mm_set_pd(5.5, 6.5);
        __m128d output = _mm_add_pd(input0, input1);
        /* OK, and this is how we get the doubles out:
        * with _mm_cvtsd_f64 + _mm_unpackhi_pd
        * https://stackoverflow.com/questions/19359372/mm-cvtsd-f64-analogon-for-higher-order-floating-point
        */
        assert(_mm_cvtsd_f64(output) == 9.0);
        assert(_mm_cvtsd_f64(_mm_unpackhi_pd(output, output)) == 7.0);
    }

    return 0;
}

GitHub上游。

paddq.c

#include <assert.h>
#include <inttypes.h>
#include <string.h>

#include <x86intrin.h>

uint32_t global_input0[] __attribute__((aligned(16))) = {1, 2, 3, 4};
uint32_t global_input1[] __attribute__((aligned(16))) = {5, 6, 7, 8};
uint32_t global_output[4] __attribute__((aligned(16)));
uint32_t global_expected[] __attribute__((aligned(16))) = {6, 8, 10, 12};

int main(void) {

    /* 32-bit add hello world. */
    {
        __m128i input0 = _mm_set_epi32(1, 2, 3, 4);
        __m128i input1 = _mm_set_epi32(5, 6, 7, 8);
        __m128i output = _mm_add_epi32(input0, input1);
        /* _mm_extract_epi32 mentioned at:
        * https://stackoverflow.com/questions/12495467/how-to-store-the-contents-of-a-m128d-simd-vector-as-doubles-without-accessing/56404421#56404421 */
        assert(_mm_extract_epi32(output, 3) == 6);
        assert(_mm_extract_epi32(output, 2) == 8);
        assert(_mm_extract_epi32(output, 1) == 10);
        assert(_mm_extract_epi32(output, 0) == 12);
    }

    /* Now from memory. */
    {
        __m128i *input0 = (__m128i *)global_input0;
        __m128i *input1 = (__m128i *)global_input1;
        _mm_store_si128((__m128i *)global_output, _mm_add_epi32(*input0, *input1));
        assert(!memcmp(global_output, global_expected, sizeof(global_output)));
    }

    /* Now a bunch of other sizes. */
    {
        __m128i input0 = _mm_set_epi32(0xF1F1F1F1, 0xF2F2F2F2, 0xF3F3F3F3, 0xF4F4F4F4);
        __m128i input1 = _mm_set_epi32(0x12121212, 0x13131313, 0x14141414, 0x15151515);
        __m128i output;

        /* 8-bit integers (paddb) */
        output = _mm_add_epi8(input0, input1);
        assert(_mm_extract_epi32(output, 3) == 0x03030303);
        assert(_mm_extract_epi32(output, 2) == 0x05050505);
        assert(_mm_extract_epi32(output, 1) == 0x07070707);
        assert(_mm_extract_epi32(output, 0) == 0x09090909);

        /* 32-bit integers (paddw) */
        output = _mm_add_epi16(input0, input1);
        assert(_mm_extract_epi32(output, 3) == 0x04030403);
        assert(_mm_extract_epi32(output, 2) == 0x06050605);
        assert(_mm_extract_epi32(output, 1) == 0x08070807);
        assert(_mm_extract_epi32(output, 0) == 0x0A090A09);

        /* 32-bit integers (paddd) */
        output = _mm_add_epi32(input0, input1);
        assert(_mm_extract_epi32(output, 3) == 0x04040403);
        assert(_mm_extract_epi32(output, 2) == 0x06060605);
        assert(_mm_extract_epi32(output, 1) == 0x08080807);
        assert(_mm_extract_epi32(output, 0) == 0x0A0A0A09);

        /* 64-bit integers (paddq) */
        output = _mm_add_epi64(input0, input1);
        assert(_mm_extract_epi32(output, 3) == 0x04040404);
        assert(_mm_extract_epi32(output, 2) == 0x06060605);
        assert(_mm_extract_epi32(output, 1) == 0x08080808);
        assert(_mm_extract_epi32(output, 0) == 0x0A0A0A09);
    }

    return 0;

GitHub上游。

第 3 步：优化一些代码并对其进行基准测试

最后也是最重要和最困难的一步，当然是实际使用内在函数来使代码更快，然后对您的改进进行基准测试。

这样做可能需要您了解一些有关 x86 微体系结构的知识，而我自己对此并不了解。 CPU 与 IO 限制可能是出现的问题之一：术语“CPU 限制”和“I/O 限制”是什么意思？

如所述：https://stackoverflow.com/a/12172046/895245 这几乎不可避免地需要阅读 Agner Fog 的文档，该文档似乎比英特尔本身发布的任何内容都要好。

不过，希望步骤 1 和 2 能够作为至少尝试功能性非性能方面并快速了解指令正在执行的操作的基础。

TODO：在这里生成一个此类优化的最小有趣示例。

Step 1: write some assembly manually

I recommend that you first try to write your own assembly manually to see and control exactly what is happening when you start learning.

Then the question becomes how to observe what is happening in the program, and the answers are:

GDB
use the C standard library to print and assert things

Using the C standard library yourself requires a little bit of work, but nothing much. I have for example done this work nicely for you on Linux in the following files of my test setup:

Using those helpers, I then start playing around with the basics, such as:

load and store data to / from memory into SSE registers
add integers and floating point numbers of different sizes
assert that the results are what I expect

addpd.S

#include <lkmc.h>

LKMC_PROLOGUE
.data
    .align 16
    addps_input0: .float 1.5, 2.5,  3.5,  4.5
    addps_input1: .float 5.5, 6.5,  7.5,  8.5
    addps_expect: .float 7.0, 9.0, 11.0, 13.0
    addpd_input0: .double 1.5, 2.5
    addpd_input1: .double 5.5, 6.5
    addpd_expect: .double 7.0, 9.0
.bss
    .align 16
    output:       .skip 16
.text
    /* 4x 32-bit */
    movaps addps_input0, %xmm0
    movaps addps_input1, %xmm1
    addps %xmm1, %xmm0
    movaps %xmm0, output
    LKMC_ASSERT_MEMCMP(output, addps_expect, $0x10)

    /* 2x 64-bit */
    movaps addpd_input0, %xmm0
    movaps addpd_input1, %xmm1
    addpd %xmm1, %xmm0
    movaps %xmm0, output
    LKMC_ASSERT_MEMCMP(output, addpd_expect, $0x10)
LKMC_EPILOGUE

GitHub upstream.

paddq.S

#include <lkmc.h>

LKMC_PROLOGUE
.data
    .align 16
    input0:       .long 0xF1F1F1F1, 0xF2F2F2F2, 0xF3F3F3F3, 0xF4F4F4F4
    input1:       .long 0x12121212, 0x13131313, 0x14141414, 0x15151515
    paddb_expect: .long 0x03030303, 0x05050505, 0x07070707, 0x09090909
    paddw_expect: .long 0x04030403, 0x06050605, 0x08070807, 0x0A090A09
    paddd_expect: .long 0x04040403, 0x06060605, 0x08080807, 0x0A0A0A09
    paddq_expect: .long 0x04040403, 0x06060606, 0x08080807, 0x0A0A0A0A
.bss
    .align 16
    output:       .skip 16
.text
    movaps input1, %xmm1

    /* 16x 8bit */
    movaps input0, %xmm0
    paddb %xmm1, %xmm0
    movaps %xmm0, output
    LKMC_ASSERT_MEMCMP(output, paddb_expect, $0x10)

    /* 8x 16-bit */
    movaps input0, %xmm0
    paddw %xmm1, %xmm0
    movaps %xmm0, output
    LKMC_ASSERT_MEMCMP(output, paddw_expect, $0x10)

    /* 4x 32-bit */
    movaps input0, %xmm0
    paddd %xmm1, %xmm0
    movaps %xmm0, output
    LKMC_ASSERT_MEMCMP(output, paddd_expect, $0x10)

    /* 2x 64-bit */
    movaps input0, %xmm0
    paddq %xmm1, %xmm0
    movaps %xmm0, output
    LKMC_ASSERT_MEMCMP(output, paddq_expect, $0x10)

LKMC_EPILOGUE

GitHub upstream.

Step 2: write some intrinsics

For production code however, you will likely want to use the pre-existing intrinsics instead of raw assembly as mentioned at: https://stackoverflow.com/a/1390802/895245

So now I try to convert the previous examples into more or less equivalent C code with intrinsics.

addpq.c

#include <assert.h>
#include <string.h>

#include <x86intrin.h>

float global_input0[] __attribute__((aligned(16))) = {1.5f, 2.5f, 3.5f, 4.5f};
float global_input1[] __attribute__((aligned(16))) = {5.5f, 6.5f, 7.5f, 8.5f};
float global_output[4] __attribute__((aligned(16)));
float global_expected[] __attribute__((aligned(16))) = {7.0f, 9.0f, 11.0f, 13.0f};

int main(void) {
    /* 32-bit add (addps). */
    {
        __m128 input0 = _mm_set_ps(1.5f, 2.5f, 3.5f, 4.5f);
        __m128 input1 = _mm_set_ps(5.5f, 6.5f, 7.5f, 8.5f);
        __m128 output = _mm_add_ps(input0, input1);
        /* _mm_extract_ps returns int instead of float:
        * * https://stackoverflow.com/questions/5526658/intel-sse-why-does-mm-extract-ps-return-int-instead-of-float
        * * https://stackoverflow.com/questions/3130169/how-to-convert-a-hex-float-to-a-float-in-c-c-using-mm-extract-ps-sse-gcc-inst
        * so we must use instead: _MM_EXTRACT_FLOAT
        */
        float f;
        _MM_EXTRACT_FLOAT(f, output, 3);
        assert(f == 7.0f);
        _MM_EXTRACT_FLOAT(f, output, 2);
        assert(f == 9.0f);
        _MM_EXTRACT_FLOAT(f, output, 1);
        assert(f == 11.0f);
        _MM_EXTRACT_FLOAT(f, output, 0);
        assert(f == 13.0f);

        /* And we also have _mm_cvtss_f32 + _mm_shuffle_ps, */
        assert(_mm_cvtss_f32(output) == 13.0f);
        assert(_mm_cvtss_f32(_mm_shuffle_ps(output, output, 1)) == 11.0f);
        assert(_mm_cvtss_f32(_mm_shuffle_ps(output, output, 2)) ==  9.0f);
        assert(_mm_cvtss_f32(_mm_shuffle_ps(output, output, 3)) ==  7.0f);
    }

    /* Now from memory. */
    {
        __m128 *input0 = (__m128 *)global_input0;
        __m128 *input1 = (__m128 *)global_input1;
        _mm_store_ps(global_output, _mm_add_ps(*input0, *input1));
        assert(!memcmp(global_output, global_expected, sizeof(global_output)));
    }

    /* 64-bit add (addpd). */
    {
        __m128d input0 = _mm_set_pd(1.5, 2.5);
        __m128d input1 = _mm_set_pd(5.5, 6.5);
        __m128d output = _mm_add_pd(input0, input1);
        /* OK, and this is how we get the doubles out:
        * with _mm_cvtsd_f64 + _mm_unpackhi_pd
        * https://stackoverflow.com/questions/19359372/mm-cvtsd-f64-analogon-for-higher-order-floating-point
        */
        assert(_mm_cvtsd_f64(output) == 9.0);
        assert(_mm_cvtsd_f64(_mm_unpackhi_pd(output, output)) == 7.0);
    }

    return 0;
}

GitHub upstream.

paddq.c

#include <assert.h>
#include <inttypes.h>
#include <string.h>

#include <x86intrin.h>

uint32_t global_input0[] __attribute__((aligned(16))) = {1, 2, 3, 4};
uint32_t global_input1[] __attribute__((aligned(16))) = {5, 6, 7, 8};
uint32_t global_output[4] __attribute__((aligned(16)));
uint32_t global_expected[] __attribute__((aligned(16))) = {6, 8, 10, 12};

int main(void) {

    /* 32-bit add hello world. */
    {
        __m128i input0 = _mm_set_epi32(1, 2, 3, 4);
        __m128i input1 = _mm_set_epi32(5, 6, 7, 8);
        __m128i output = _mm_add_epi32(input0, input1);
        /* _mm_extract_epi32 mentioned at:
        * https://stackoverflow.com/questions/12495467/how-to-store-the-contents-of-a-m128d-simd-vector-as-doubles-without-accessing/56404421#56404421 */
        assert(_mm_extract_epi32(output, 3) == 6);
        assert(_mm_extract_epi32(output, 2) == 8);
        assert(_mm_extract_epi32(output, 1) == 10);
        assert(_mm_extract_epi32(output, 0) == 12);
    }

    /* Now from memory. */
    {
        __m128i *input0 = (__m128i *)global_input0;
        __m128i *input1 = (__m128i *)global_input1;
        _mm_store_si128((__m128i *)global_output, _mm_add_epi32(*input0, *input1));
        assert(!memcmp(global_output, global_expected, sizeof(global_output)));
    }

    /* Now a bunch of other sizes. */
    {
        __m128i input0 = _mm_set_epi32(0xF1F1F1F1, 0xF2F2F2F2, 0xF3F3F3F3, 0xF4F4F4F4);
        __m128i input1 = _mm_set_epi32(0x12121212, 0x13131313, 0x14141414, 0x15151515);
        __m128i output;

        /* 8-bit integers (paddb) */
        output = _mm_add_epi8(input0, input1);
        assert(_mm_extract_epi32(output, 3) == 0x03030303);
        assert(_mm_extract_epi32(output, 2) == 0x05050505);
        assert(_mm_extract_epi32(output, 1) == 0x07070707);
        assert(_mm_extract_epi32(output, 0) == 0x09090909);

        /* 32-bit integers (paddw) */
        output = _mm_add_epi16(input0, input1);
        assert(_mm_extract_epi32(output, 3) == 0x04030403);
        assert(_mm_extract_epi32(output, 2) == 0x06050605);
        assert(_mm_extract_epi32(output, 1) == 0x08070807);
        assert(_mm_extract_epi32(output, 0) == 0x0A090A09);

        /* 32-bit integers (paddd) */
        output = _mm_add_epi32(input0, input1);
        assert(_mm_extract_epi32(output, 3) == 0x04040403);
        assert(_mm_extract_epi32(output, 2) == 0x06060605);
        assert(_mm_extract_epi32(output, 1) == 0x08080807);
        assert(_mm_extract_epi32(output, 0) == 0x0A0A0A09);

        /* 64-bit integers (paddq) */
        output = _mm_add_epi64(input0, input1);
        assert(_mm_extract_epi32(output, 3) == 0x04040404);
        assert(_mm_extract_epi32(output, 2) == 0x06060605);
        assert(_mm_extract_epi32(output, 1) == 0x08080808);
        assert(_mm_extract_epi32(output, 0) == 0x0A0A0A09);
    }

    return 0;

GitHub upstream.

Step 3: go and optimize some code and benchmark it

The final, and most important and hard step, is of course to actually use the intrinsics to make your code fast, and then to benchmark your improvement.

Doing so, will likely require you to learn a bit about the x86 microarchitecture, which I don't know myself. CPU vs IO bound will likely be one of the things that comes up: What do the terms "CPU bound" and "I/O bound" mean?

As mentioned at: https://stackoverflow.com/a/12172046/895245 this will almost inevitably involve reading Agner Fog's documentation, which appear to be better than anything Intel itself has published.

Hopefully however steps 1 and 2 will serve as a basis to at least experiment with functional non-performance aspects and quickly see what instructions are doing.

TODO: produce a minimal interesting example of such optimization here.

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